Treatment of hydrocarbons



- Patented Jan. 15 1946 TREATMENT OF HYDBOCARBONS Aristid V. Grosse, Bronxvilie, N. Y., and Carl B. Linn, Riverside, Iil., assignors to Universal Oil Products Company, Chicago, 11L, a corporation of Delaware No Drawing. Application August 30, 1943, Serial No. 500,552

11 Claims. (Cl. 260683.4)

This is a continuation-in-part of our co-pending application Serial No. 416,862, flled October 28, 1941, which is in turn a continuation-in-part of our application Serial No. 299,108, filed October 12, 1939, and which is also a continuation-in-part of our application Serial No. 248,777, filed December 31, 1938 now Patent No. 2,267,730, granted December 30, 1M1.

This invention relates to a process for treating hydrocarbon mixtures to remove fluorine therefrom. More specifically it relates to the treatment of synthetic hydrocarbons produced in the boron fluoride.

oleflnic hydrocarbons to produce saturated liquid hydrocarbons utilizable as gasoline motor fuels with high antiknock properties, is a recent development which is beginning to assume commercial importance. By this means relatively lowboiling isoparaflinic hydrocarbons may be alkylated with low-boiling oleflns,thereby converting materials which have relatively low-commercial value into hydrocarbons with high antiknock values, said hydrocarbons being particularly useful as components of aviation gasoline.

Active fluoride catalysts including hydrogen fluoride, hydrofluoricacid and mixtures comprising essentially hydrogen fluoride and boron trifluoride are used in the alkylation of saturated hydrocarbons including isoparaflins and certain I naphthenic hydrocarbons by oleflns, but it has been found that the resultant alkylation product frequently contains minor quantities of fluorine in combination-with some of the hydrocarbon radicals, possibly due to interaction of hydrogen fluoride with oleflnic constituents of the reaction mixture. Boron fluoride assists hydrogen fluoride in catalyzing the alkylation of an isoparamn by ethylene and higher oleflns, but in this case also the product contains small quantities of fluorides as do those formed in the presence of hydrogen fluoride, from an isoparafiin and an olefin of higher molecular weight than ethylene.

Although the fluorine content or the hydrocarbon product of gasoline boiling range is rarely I The alkylation of branched chain paramnic hydrocarbons such as isobutane and isopentane with erally expressed by the term "octane number, is

considerably reduced either when the gasoline is used as such, or when a small amount of an anti-' detonating agent such as lead tetraethyl is added thereto. Thus it may be shown that a gasoline fraction containing as much as 0.1% by weight of fluorine has inferior antiknock properties particularly as concerns its response to lead tetraethylv as compared to the otherwise same material which contains substantially no fluorine compounds. The present invention oflers a method for reducing the, fluorine content of the hydrocarbon alkylation product to a point where this adverse I effect is no longer substantial.

Broadly, the invention comprises contacting hydrocarbons containing organically combined fluorine with porous carbon in the presence of a minor amount of hydrogen fluoride whereby to remove said combined fluorine.

In one specific embodiment the present invention comprises a process for treating hydrocarbons produced by catalytic alkylation of isoparaflins with oleflns in the presence of an active fluoride catalyst, by contacting said hydrocarbons with activated carbon in the presence of minor amounts of hydrogen fluoride under dehydrofluorinating conditions of temperature and pressure, and recovering the-treated hydrocarbon.

The carbon contact agent may be prepared from any of a number of available forms of carbon, e. g., coke, graphite, charcoal, carbon black. -etc., but as a general requirement the contact mass should possess a porous structure. Granular coke and charcoal in their usual forms are usually sufliciently porous for. direct use, but in the case of graphite or certain other 'forms'of carbon it is generally desirable to prepare porous contact masses, e. an, by admixing carbon particles and a binder, forming into suitable contact and yields a substantially fluorine-free hydrocarbon product.

In operating the present process it is generally advisable to employ at least two contactors containing porous carbon so that one may be iii-use while the other is being heated and/or evacuated to remove therefrom the hydrogen fluoride ad- 'sorbed upon the carbon during the treating perid. The hydrogen fluoride or a mixture of hyder revised conditions of operation. At higher temperatures higher space velocities are employed. The term liquid space velocity" refers to the volume of liquid hydrocarbon product charged per volume of granular activated carbon per hour. The pressure used during defluorination treatment may be atmospheric, subatmospheric, or superatmospheric, the last-named being used mainly in the interest of increasingthe treating capacity of the apparatus employed, even though the defluorination reaction is favored by lower pressures.

The term "activated carbon" as used in the present specification and claims is intended to include any ty e of prepared carbon or carbonaceous material which is more or less granular and possessed of good porosity and structural stren th and which has been prepared by general steps involving the leaching of adsorbed materials from granular residual carbonaceous materials such as wood c ar and various varieties of coke by mineral acids and by the controlled heating. preferably under vacuum. to ex el adsorbed licuids and gases. It is reco nized that various forms of active granular carbon will varv considerably in their adsorntive capacities and therefore in the amounts of hydrogen'fluoride that they will adsorb and retain.

We have found that or anic fluoride-containing compounds present in alkylation roducts formed by interaction of isooarafflns with olefins in the presence of active fluoride catalysts containing hydro en fluoride are converted into substantial amounts of saturated hydrocarbons and hydro en fluoride by contact under the above indicated treating conditions with activated charcoal and other forms of activated carbon.

While the following concept should not be mis-' construed to limit the invention, it is likely that the adsorbed condition functionsfurther to decompose alkyl fluorides and liberate hydrogen fluoride. This reaction may involve the conversion'oi' an alkyl fluoride molecule into a molecule each of olefin andhydrogen fluoride.

The olefin so liberated in the presence of hydrogen fluoride is able to combine with a molecule of an isoparaffln to produce a molecule of a higher boiling parafilnic hydrocarbon. Thus the combined action of hydrogen fluoride dissolved in the alkylation product and of an added activated or porous carbon effects decomposition of alkyl fluorides 1. A process for purifying a drogen fluoride and boron trifluoride (in' case alkylation is effected in the presence of the mixed catalyst) so recovered may be recycled to further use in the process as alkylating catalyst.

The following example is given to show results obtained in the operation of the process, but should not be considered to unduly limit the broad scope of the invention.

A liquidmixture of isobutane and isobutene containing 36% by volume of the latter was charged to a reactor of 1000 volumes capacity containing 212 volumes of anhydrous hydrogen fluoride maintained at 30 C. under the vapor pressure of the total mixture. No additional hydrogen fluoride was added during the run while i fluoride was then withdrawn from near the top of the reactor into a contactbr containing a fixed bed of activated charcoal. dissolved in the hydrocarbon mixture was retained by the activated charcoal and substantial amounts of alkyl fluorides were also removed from the hydrocarbon product. Thus the fluorine-content of the butane-free alkylation product was less than 0.01% after the charcoal treatments. Alkylation product which had not been so treated with activated charcoal but which had been freed from dissolved hydrogen fluoride by washing with caustic and water contained about 0.2% of organically combined fluorine.

The character of the present invention and particularly its practical value are evident from the preceding specification and example given.

We claim as our invention:

' hydrocarbon mixture containing as an impurity a relatively small percentage of organically combined fluorine to remove fluorine therefrom which comprises contacting said mixture with activated carbon in the presence of a minor amount of hydrogen fluoride under dehydrofluorinating conditions of ternperature and pressure, and recovering the treated hydrocarbon mixture.

2. A process for purifying a hydrocarbon mixture containing as an impurity a relatively small- Hydrogen fluoride pressure, and recovering the treated hydrocarbon mixture.

with activated carbon in the presence of a minor amount of hydrogen fluoride under dehydrofluorinating conditions of temperature and pressure, and recovering the treated hydrocarbon mixture.

5. A process for purifying a hydrocarbon mixture containing as an impurity a relatively small percentage of dissolved organic fluorine compounds and produced by catalytic alkylation of an isoparaflinic hydrocarbon with an olefinic hydrocarbon in the presence of an active fluoride catalyst which comprises, contacting said mixture with activated carbon in the presence of a minor amount of hydrogen fluoride at a temperature of from about 20 to about 150 C., and recovering the treated hydrocarbon mixture.

6. In a process for alkylating an isoparaflinic hydrocarbon with an olefinic hydrocarbon in the presence of an active fluoride catalyst containing hydrogen fluoride, the improvement which comprises separating a substantial proportion of the catalyst from a reaction mixture comprising essentially a substantially saturated alkylate, unconverted isoparaiflnic hydrocarbon, dissolved hydrogen fluoride, and small amounts of organic fluorine compounds. mixture with activated carbon under dehydrofluorinating conditions of temperature and pressure, and recovering the treated hydrocarbons.

7. In a process for alkylating an isoparaflinic hydrocarbon with an oleflnic hydrocarbon in the presence of an active fluoride catalyst containing hydrogen fluoride, the improvement which comprises separating a substantial proportion of the catalyst from a reaction mixture comprising a substantially saturated alkylate, unconverted isoparamnic hydrocarbon, dissolved hydrogen fluoride, and small amounts of organic fluorine compounds, and contacting said reaction mixture with contacting said reaction activated carbon at a temperature of from about 20 to about 150 C. to remove therefrom substantially all fluorine compounds.

8. A process for purifying a hydrocarbon mixture containing as an impurity a relatively small percentage of organically combined fluorine to remove fluorine therefrom which comprises contacting said mixture with porous carbon in the presence of a minor amount of hydrogen fluoride under dehydrofluorinating conditions of temperature and pressure, and recovering the treated hydrocarbon mixture.

9. A process for purifying a hydrocarbon mixture containing as an impurity a relatively small percentage of dissolved organic fluorine compounds and produced by catalytic alkylation of an isoparamnic hydrocarbon with an-oleflnio hydrocarbon in the presence of an active fluoride catalyst which comprises, contacting said mixture with porous carbon in the presence or a minor amount of hydrogen fluoride under dehydrofluorinating conditions of temperature and pressure, and recovering the treated hydrocarbon mixture.

10. A process for purifying a hydrocarbon mixture containing as an impurity a relatively small percentage of dissolved organic fluorine compounds which comprises, contacting said mixture with porous carbon in the presenc of a minor amount of hydrogen fluoride at a temperature of from about 20 to about 150 C., and recovering the treated hydrocarbon mixture.

11. In a process for alkylating an isoparafiinic hydrocarbon with an oleflnic hydrocarbon in the presence of an active fluoride catalyst containing hydrogen fluoride, the improvement which comprises separating a substantial proportion of the catalyst from a reaction mixture comprising essentially a substantially saturated alkylate, unconverted isoparaflinic hydrocarbon, dissolved hydrogen fluoride, and small amounts of organic fluorine compounds, contacting said reaction mixture W113i porous carbon under dehydrofluorinating conditions of temperature and pressure, and recovering the treated hydrocarbons.

ears'rm v. GROSSE. CARL B. LINN. 

